Season 21 of “The Voice” kicked off with a star-studded concert.

Coaches Blake Shelton, John Legend, Kelly Clarkson and new coach Ariana Grande treated the audience to Aretha Franklin’s “Respect” and Sam & Dave’s “Hold On, I’m Coming”.

“The Voice” also posted a behind the scenes video after their performance.

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“We just sang out coach performance and I’m shaking,” Grande said.

“You’ve never lived life until you’ve heard John Legend, Blake Shelton and Kelly Clarkson in your inner ears like that,” she added, pointing to her ear pieces.

On “The Kelly Clarkson Show” on Friday, Clarkson spoke with her fellow “The Voice” coach Grande about how the other coaches feel about her joining the show for Season 21.

“Blake and John, they are terrified of you,” Clarkson, 39, told Grande, 28. After playing a clip of Shelton unconvincingly denying that he is afraid of Ariana’s die-hard fans (who call themselves Arianators), Clarkson turned to her in-studio audience, saying, “[Blake] is so afraid of Ariana’s fan base.”

Grande humbly played down her chance at winning.

RELATED: Kelly Clarkson Tells Ariana Grande That John Legend And Blake Shelton Are ‘Terrified’ Of Her On ‘The Voice’

Season 21 of “The Voice” starts on Monday, Sept 20 on NBC at 8 p.m. PT/ET.